The Effect of Particle Strength on the Ballistic Resistance of Shear Thickening Fluids

The response of shear thickening fluids (STFs) under ballistic impact has received considerable attention due to its field-responsive nature. While efforts have primarily focused on the response of traditional ballistic fabrics impregnated with fluids, the response of pure STFs to penetration has received limited attention. In the present study, the ballistic response of pure STFs is investigated and the effect of fluid density and particle strength on ballistic performance is isolated. The loss of ballistic resistance of STFs at higher impact velocities is governed by particle strength, indicating the range of velocities over which they may provide effective armor solutions.Comment: 4 pages, 4 figure

Capturing Genetic Variation during Ecological Restorations: An Example from Kankakee Sands in Indiana

Genetic variation in populations, both natural and restored, is usually considered crucial for response to short term environmental stresses and for long term evolutionary change. To have the best chance of successful long-term survival, restored populations should reflect the extant variation found in remnants, but restored sites may suffer from genetic bottlenecks as a result of founder effects. Kankakee Sands is a large-scale restoration being conducted by The Nature Conservancy (TNC) in northwestern Indiana. Our goal was to test for loss of genetic variation in restored plant populations by comparing them with TNC’s seed source nursery and with local remnant populations that were the source of nursery seed and of the first few restored sites. Allozyme analysis of Baptisia leucantha, Asclepias incarnata, Coreopsis tripteris, and Zizia aurea showed low levels of allozyme diversity within all species and reductions in polymorphism, alleles per locus, and expected heterozygosity between remnants and restorations for all species except A. incarnata. Almost all lost alleles were rare; restored populations contained almost 90% of alleles at polymorphic loci that occurred in remnants at frequencies greater than one percent. Allele frequencies for most loci did not differ between remnants and restored sites. Most species showed significant allele frequency differentiation among remnant populations and among restored sites. Our results indicate that seed collection techniques used at Kankakee Sands captured the great majority of allozyme variation present in seed source remnant populations

Novel group 9 catalysts for the carbonylation of methanol

The carbonylation of methanol catalysed by Group 9 metals is the principle industrial route to acetic acid. It has been one of the most important applications of homogeneous catalysts for thirty years. In that time the preferred catalytic species has descended the group from cobalt, through rhodium, and recently to iridium with the introduction of B.P. Chemical's Cativa process. Rhodium and iridium are precious metals, it would be advantageous to develop a catalytic system which does not depend on a rare metal. One way this could be achieved is by improving cobalt catalysed carbonylation. Work has concentrated on the ability of the cyclopentadienyl, pentamethylcyclopentadienyl and triethyl phosphine ligands to promote cobalt catalysts. Several novel cobalt catalysts and one novel rhodium catalyst have been discovered for the carbonylation of methanol to methyl acetate. CH₃OH + ROH Co/Catalyst-→ CH₃COOR + H₂O At 120°C using [Cp*Co(CO)₂] and Pet₃ as catalyst precursors rates of methanol carbonylation have been achieved which are, to our knowledge, far greater than any previously reported for cobalt catalysts. The initial rate of carbonylation compares favourably with that of rhodium based systems. High Pressure Infrared Spectroscopy has been utilised extensively as a tool for investigating the solution behaviour of the novel catalyst precursors [CpCo(CO)PMe₂ph], [CpCo(CO)₂], [Cp*Co(CO)₂] and [Cp*Rh(C0)₂]